One of the primary factors in assessing specific mechanisms of brain aging is high quality animal care.[unreadable] One of the most common confounding variables in aging studies are inconsistent animal care, non-specific[unreadable] stress, and the presence of unrecognized age-related pathologies that compromise the dependent variables[unreadable] under investigation. For these reasons (and others), the Animal Core within the PPG must be of the highest[unreadable] quality. In the past funding period, this Core has been successful in maintaining animals in specific[unreadable] pathogen free (SPF) conditions for project studies, in developing and providing extensive validation of a[unreadable] novel model of adult-onset growth hormone deficiency that will continue to be used in the proposed funding[unreadable] period. This model provides a unique resource for the Program Project and opportunity to investigate the[unreadable] effects of growth hormone deficiency apart from other factors that may contribute to brain aging. The Animal[unreadable] Core has multiple aims: 1) The Core will procure and maintain animals used by program investigators and[unreadable] meet all AAALAC and institutional standards for animal care in the satellite facilities. The Core will also[unreadable] maintain a breeding colony of dw/+ (female) and dw/dw (male) Lewis rats and raise offspring to be used for[unreadable] the model of adult-onset growth hormone deficiency proposed in this application. The Core will coordinate[unreadable] animal/tissue use among the projects. 2) The Core personnel will assess basic parameters of aging animals[unreadable] and monitor sentinel and experimental animals for the presence of disease. 3) The Core will provide surgical[unreadable] services. 4) The Core will be responsible for irradiation of animals, as necessary, and measure hormone[unreadable] levels in tissue. 5) The Core will conduct behavioral analyses on animals to assess age-related alterations in[unreadable] hippocampally dependent measures of learning and memory and will develop frontal-lobe dependent tasks[unreadable] of learning and memory. The Animal Core is an essential aspect of the Program Project ensuring effective[unreadable] management of limited resources, smooth interactions between projects and the use of animal models that[unreadable] have been extensively validated for studies of the biology of aging.